This invention relates in general to hollow cylindrical member support apparatus and more specifically to a hollow cylindrical member supporting end flange, a hollow cylindrical member assembly containing the end flange and methods for fabricating and using the hollow cylindrical member assembly.
A photoreceptor conventionally utilized for copiers and printers comprises a hollow electrically conductive drum substrate which has been dip coated with various coatings including at least one photoconductive coating comprising pigment particles dispersed in a film-forming binder. These drum type photoreceptors are usually supported on an electrically conductive shaft by drum supporting hubs or end flanges. The hubs are usually constructed of plastic material and have a hole through their center into which a supporting axle shaft is inserted. Since hubs are usually constructed of electrically insulating plastic material, an electrical grounding means comprising a flexible spring steel metal strip is secured to the hub and positioned to contact both the electrically conductive axle shaft and the electrically conductive metal substrate of the photoreceptor drum. One type of grounding means is illustrated in U.S. Pat. No. 4,561,763. This metal ground strip is often bent out of alignment when inserted into one end of a photoreceptor drum. Such misalignment can result in the metal strip not contacting the interior of the drum or the axle or both after insertion of the hub into the end of the drum is completed. Further, coatings electrically insulating in the dark that are formed on the surface of the interior of the drum during dip coating can adversely affect electrical grounding of the drum to the electrically conductive drum axle shaft. If inadequate electrical grounding of the drum to the axle shaft is detected after the drum has been inserted into a modular replacement unit in which photoreceptor and various other subsystems such as cleaning and charging units are permanently mounted, repair of the drum is usually impossible without destruction of the module.
Often the hub or end flange is secured to the end of the drum by a thermosetting resin adhesive. The use of an adhesive increases the number of steps and complexity of equipment required to assemble and disassemble a hub and cylindrical member assembly. Recycling of used drums having glued hubs is difficult, if not impossible, because of damage to the hub or the drum or both during removal of the hub from the drum by common techniques such as by hammering. Such removal techniques damage or destroy both the drum and the hub. Further, where disassembly is accomplished without damage, cleaning of both the hub and the cylindrical substrate is required to remove adhering adhesive. In addition, adhesive application equipment utilized during mounting of an end flange to a cylindrical substrate are difficult to maintain because the adhesive has a short pot life and often solidifies and clogs the equipment thereby requiring time consuming efforts to clean and remove the solidified adhesive. The use of bolts and nuts to secure hubs to drums requires time intensive activity and does not address the problem of electrically grounding a drum substrate to the drum axle shaft.
Another type of hub avoids the need for an adhesive by utilizing resilient fingers having pointed tips that dig into and penetrate the inner surface of the drum. This hub is described in U.S. Pat. No. 5,357,321, the entire disclosure thereof being incorporated herein by reference. The hub provides excellent support for the drum. However, the pointed tips can form scratches and grooves in the interior surface of the drum during installation, use and removal. These scratches or grooves can adversely affect recycling of the cylindrical substrate. For example, in processes for dip coating a hollow cylindrical substrate such as a drum, the substrate is immersed in a coating solution by vertically moving the substrate in a direction parallel to the axis of the substrate. To avoid coating the interior of the hollow substrate, an expandable mandrel is usually employed to grip and seal off the upper end of the drum during the immersion coating process. Sealing of the upper end of the cylindrical substrate traps air within the interior of the cylindrical substrate below the mandrel during the coating operation thereby preventing any significant entry and deposition of the coating material within the hollow interior of the cylindrical substrate during the dip coating operation. However, scratches or grooves in the upper end of the interior of the cylindrical substrate interferes with the establishment of an airtight seal thereby allowing air to leak out from the interior of the cylindrical substrate past the mandrel seal. This allows undesirable entry and deposition of the coating material within the interior of the cylindrical substrate during dip coating operations.
Thus, there is a continuing need for improved photoreceptors that are more reliable and facilitate recycling.